PLATE 18 



EXPLANATION OF FIGURES 



Fig. 23 Photomicrograph of a transverse section taken through the siibocuhir 

 lymph sacs [1) of a fifteen-day steelhead trout embrj-o. P. E. C. 726, slide 1, 

 section 78; injected embryo. 



Fig. 24 Photomicrograph of a transverse section taken through the subocular 

 lymph sacs (1) of a sixteen-day rainbow trout embryo at the level of the infra- 

 orbital veins (28); showing that the veins are fully injected and that none of the 

 injecta has passed into the sacs. P. E. C. 751, slide 1, section 66. 



REFERENCES 



1, vSubocular lymph sac 22, Carotid artery 



6, Precardinal or jugular vein 23, Infraorbital vein 



15, Hyoidean artery 28, Infundibulum 



20, Caudal end of eye 



110 



